This invention relates to physiologically acceptable and non-corrosive acidic silicone compositions and a method for treating surfaces such as glass, porcelain, ceramic, polished or painted metal, plastic, and the like, to render them water and soil repellent. Volatile organic compound (VOC) free cream, paste, powder and solid compositions are provided. These acidic silicone compositions are non-toxic, non-irritating, non-corrosive and free of volatile organic compounds. They also allow treated surfaces to be effectively cleaned with only plain water, mild soap or detergent solutions and without the need to use acidic, caustic or abrasive cleaners.
There has been extensive research and development involving silicone compositions for rendering nonporous surfaces water repellant. U.S. Pat. No. 2,612,458 (Stedman) discloses the application of substituted polysilicanes to windshields to achieve repellency. U.S. Pat. No. 2,923,653 (Matlin) discloses improved compositions employing alkoxy groups in the polysilicane to improve the repellency. U.S. Pat. No. 2,962,390 (Fain, et al.) describes a paste containing a solid rubbing agent and an alkyl alkoxy silane which when rubbed on a glass surface provides repellency. U.S. Pat. No. 3,244,541 (Fain, et al.) discloses acidic solutions of alkyl alkoxy silane monomers that produce rain repellent films on glass and which are also solvent resistant.
U.S. Pat. No. 3,579,540 (Ohlhausen) discloses water repellent film-forming compositions of alkylpolysiloxanes and acid or alkylpolysiloxanes, acid and solvent which result in durable and effective water repellent films on nonporous substrates. This patent also discloses the importance of adding the acid to the alcohol to form the intermediate half ester and then to add the alkylpolysiloxane in order to solublize the alkylpolysiloxane and eliminate the formation of two or three phases in the mixture. It also discloses that the alkylpolysiloxanes can be employed with solvents, diluents and extenders including colloidal pyrogenic silicas and clays. Isopropyl alcohol solvent was preferred. U.S. Pat. No. 3,817,769 (Fisher) discloses a rapid curing repellent composition by use of dyes, i.e., methylene blue, to give a durable and tough polysiloxane film. However, films prepared in accordance with Fisher""s examples gave poor repellency results unless sulfuric acid was also incorporated in the composition. U.S. Pat. No. 3,998,643 (Liddle), discloses the addition of hydrogen fluoride to the Ohlhausen compositions and processes with claimed improved repellency and durability.
U.S. Pat. No.5,021,089 (Uwata, et al.), discloses a water repellent composition comprising a volatile organic solvent, a silyl phosphate and an organopolysiloxane, thus eliminating the mineral acid required in previously disclosed water repellent compositions. U.S. Pat. No. 5,417,744 (Gasmena) discloses a composition containing a fluorinated polysiloxane, a polysiloxane, a polyester modified polysiloxane, an acid, water and an alcohol to obtain an optically clear coating having hydrophobic properties. U.S. Pat. No. 5,584,917 (Kijima) discloses a water repellent composition comprising an amino group-containing polyorganosiloxane, an organic acid, a surfactant and an aqueous solvent. U.S. Pat. No. 5,697,991 (Frazer) discloses an alkypolysiloxane, mineral acid, solvent and a mild abrasive (0.5-3.0%, preferred 1%) as an improved water repellent treating compound wherein the abrasive serves to enhance dirt and grit removal. U.S. Pat. No. 5,759,618 (Taylor) discloses a strong phosphoric acid, hydrofluoric acid, sulfuric acid cleaning solution for glass surfaces prior to the application of an excess of an alkoxysilane/sulfuric acid solution to the glass surface with timing, temperature and humidity being critical for the removal of the excess in order to achieve an abrasive resistant, water repellent coating on the surface of the glass.
U.S. Pat. No. 4,005,030 (Heckert, et al.) discloses a detergent composition containing an anionic detergent and an organosilane capable of imparting soil release benefits to hard surfaces washed with the detergent solution. However, repeated washing will subsequently remove the coating. U.S. Pat. Nos. 5,900,459 and 6,107,399 (Selley, et al.) describe an aqueous silicone emulsion for improving the release and antideposition character of a hard impermeable surface such as automobile front ends so that the treated surfaces are easier to clean and do not require as much scouring, scraping or soaking to clean. U.S. Pat. No. 6,074,470 (Fisher, et al.) describes stable aqueous emulsions of alkoxysilanes which render porous inorganic substrates such as masonry, cement, stone, insulation products or wood water repellent by brush coating, roller coating, spraying or mixing with uncured concrete. Although silicone emulsions can penetrate and cure within porous substances, they generally require extended time for evaporation of the water phase to adhere strongly to the surface, are not long lasting and exhibit poor resistance to incidental or intentional contact with soaps, solvents, detergents and other chemicals.
After almost three decades of research and development in water repellent silicone coatings, the dominant technology has involved the use of acidified solvent-based silicone compositions. A multitude of commercial products have been formulated and marketed utilizing some form of alkylsiloxane at about a 10% concentration and a mineral acid at about a 1% concentration and an alcoholic solvent. These alcoholic solutions all yield water repellent coatings on nonporous surfaces, particularly glass surfaces, by application directly onto the surface, usually by rubbing with a paper towel or cloth. Upon evaporation of the alcohol, a hazy film remains which is further polished with a dry wipe material to achieve the desired transparent water repellent coating. During the application process, the odor of the evaporating alcohol can be objectionable, particularly in the confined quarters of a shower or bathroom. OSHA recommends human exposure limits for most alcohols and other solvents to minimize health concerns, i.e., isopropanol (OSHA PEL:TWA 400 ppm, STEL 500 ppm) and ethanol (OSHA PEL:TWA 1000 ppm). These volatile solvents also contribute to air pollution and are considered to be undesirable volatile organic compounds (VOCs) by regulating authorities. These solvents have storage and handling limitations because they are also flammable and could ignite during application or form explosive mixtures if the vapors are confined.
Solvent-based silicone compositions currently have limited industrial and consumer applications due to their flammability and the toxic vapor exposure to the workers. These solvent-based silicones require additional capital expenditures for explosion proof application equipment, exhaust equipment for vapor removal and scrubbing, and the monitoring of user exposure to the solvent vapors.
The application of solvent-based silicone compositions utilizes excessive amounts of silicone per square foot of coverage provided due to the evaporation of the solvent and absorption of the silicone by the wipe material. Excessive amounts of the silicone remains in the wipe material and cannot be applied to the surface to be treated. The presence of solvents can also be incompatible with gaskets, paint, etc., associated with the surface being treated. Thus, a need exists for a water repellent composition that eliminates solvents and utilizes the silicone more effectively and economically.
The application of solvent-based silicone compositions also requires time for evaporation of the solvent and results in a hazy water repellent coating which is attributable to the separation of the acid, usually sulfuric acid, from the silicone on evaporation of the solvent. The resulting haze requires removal by a second polishing step or washing and drying of the surface in order to achieve an optically clear coating. Thus, it is desirable to provide a composition that produces an optically clear water and soil repellent coating without excessive waiting, manpower or additional cleaning.
The haze which develops upon application of a solvent based system to a nonporous surface and evaporation of the compatibilizing solvent results from the development of a silicone phase and a strong acid phase. This haze must then be wiped and/or polished in order to intimately mix the silicone and acid phases onto the surface to remove the excess of the two phases and render it optically clear, and water and soil repellent.
Solvent-based silicone compositions also have storage temperature limitations. For example, ethanolic compositions in closed containers cannot be stored at temperatures above 120xc2x0 F. and have been reported to xe2x80x9cexplodexe2x80x9d due to the high storage temperatures that can sometimes occur in warehouses or during transport in closed trucks and the like which results in an increase in the internal vapor pressure in the container leading to rupture. Not only does this cause a loss of product and packaging material but it presents a potential hazardous flammable and/or explosive event. There further exists a need for a water repellent silicone composition which is free of volatile organic compounds (VOCs), or VOC compliant, and which is nonhazardous.
Most solvent-based silicone compositions contain the active silicone ingredients at about a 10%/wt level. Thus, almost 90% of the composition is solvent and this requires a large container in order to deliver the product to the customer. The larger container in turn requires more packaging material, larger boxes, more warehouse space, higher shipping costs and more shelf space. It would be very desirable to provide a concentrated silicone composition which has associated with it reduced manufacturing, packaging, storage, transportation and related sales costs, and which provides significantly fewer ounces used per square foot of coverage on the surface to the treated.
When dilute solvent-based silicone compositions are applied to a hard surface and wiped to a polished water repellent coating, the silicone coating is very thin, on the order of a mono molecular layer. These thin coatings will not hide the fine scratches and other defects in the hard surface that has been coated. It would also be desirable to provide a silicone coating composition which will leave an optically clear multimolecular layer which can hide or fill the fine scratches and other defects in the nonporous surface being coated and which results in a restored appearance to the surface.
In view of the above state of the art on research and development of water and soil repellent silicone compositions, a number of improvements are needed.
In the above-identified related patent application, essentially solventless water and soil repellent compositions for treating nonporous surfaces were disclosed. Cream, paste and powder forms of these compositions were also disclosed. These compositions consist essentially of a multi-phase dispersion of a silicone and an acid. A solid stabilizer is distributed in the multi-phase dispersion in an effective amount to stabilize the dispersion against separation. These new silicone compositions thereby overcome the many disadvantages presently associated with solvent-based silicone compositions as set forth in the background of this invention.
This invention is directed to further improvements in the compositions and methods disclosed in the above-identified related application. In particular, physiologically acceptable and non-corrosive compositions are intimate mixtures of silicone, acid and particulate solid in relative amounts to obtain the benefits of water and soil repellency. However, the acid is essentially sequestered in the composition to render it physiologically acceptable to epithelial tissue. The acidic composition is also rendered non-corrosive. The acid forms a chemical and/or physical complex with the silicone and particulate solid stabilizer components of the composition until the acid is activated by application of the composition to a surface to render it water and soil repellent. The physiologically acceptable and non-corrosive properties of the composition are satisfied by tests that prove the compositions to be non-irritating to eyes and skin, non-toxic by ingestion and non-corrosive. For example, the compositions of this invention are physiologically acceptable to epithelial tissue in accordance with the Code of Federal Regulations, 16 CFR 1500. Moreover, the compositions are also non-corrosive, for example, in that they do not exhibit a corrosion rate on steel or aluminum surfaces in accordance with the established hazardous material regulations and procedures referenced. An acceptable test for non-corrosiveness is described in 49 CFR xc2xa7173.137(c)(2), ASTM G31-72 (reapproved in 1995). Another test described hereinafter as the xe2x80x9cAcid Availability Test (xe2x80x9cAATxe2x80x9d), is a measure of the readily available acid and correlates to the physiologically acceptable or non-corrosive properties of the compositions.
The water and soil repellent compositions of this invention are useful for treatment of a variety of nonporous and porous surfaces including glass, porcelain, ceramic, marble, granite, polished or painted (coated) metal, plastic, wood, leather, concrete, textile, and the like, to render them water and soil repellent. The existing needs in the consumer, commercial and industrial fields are fulfilled by compositions of this invention because they are also VOC free or VOC compliant, economical, non-flammable, non-combustible, practical, easy to apply, haze-free upon application, capable of homogeneous delivery of the active ingredients and offer improved water/soil repellency qualities.
In another embodiment, the water and soil repellent compositions of this invention are formulated and used in the physical form of a cream, paste or powder. In this embodiment, an additive may be used, as described hereinafter, to dilute the silicone and/or the acid phase of the composition. However, in any of these physical forms, the particulate solid stabilizer compatibilizes the components or phases against separation. These forms of the silicone compositions enable multi-molecular and transparent coatings to be formed on a variety of nonporous surfaces. Furthermore, these multi-layered coatings hide or fill fine scratches and other defects in the nonporous surface being coated. Thus, the compositions and methods of this invention enable the restoration of nonporous surfaces, such as glass, which develop fine scratches and other defects in use.
Methods of preparing physiologically acceptable and non-corrosive compositions are also provided by this invention. In the solventless compositions, silicone compounds and neat acid (without solvent) are mixed with a particulate solid stabilizer in an effective amount to compatibilize or couple the components in a homogeneous mixture. In some cases, it may be desirable to heat the mixture and/or employ high-shear mixing to achieve the desired intimate blending of the components to ensure stabilization. It has been found necessary to intimately mix the components in the composition to achieve physiological acceptability and non-corrosiveness as measured by any one or more of the tests described hereinafter by 16 CFR 1500, ASTM G3-72 and the Acid Availability Test. The necessary intimate mixing is provided by any one of a number of mixers or shearing devices. Examples of a number of mixers include homogenizers and/or rotator/stator/high shear mixers that achieve satisfactory homogenization to sequester the acid in the composition. Various forms of shear or homogenization can be achieved by different means including milling, high-pressure homogenization, ultrasonication, microfluidization, high-speed blenders, ball milling, attrition, cavitation, impaction, and the like.
The resulting composition of silicone liquid, acid and stabilizer, may be a cream, paste, powder or solid, depending upon the most desired form for the intended application. It has been found that a particulate solid stabilizer is most advantageously employed in the form of fine particles. The fine particles enable the intimate delivery of the silicone and acid in the proper proportion to the surface to be treated. The solid stabilizer is contained in an amount from about 5 to about 90 percent by weight of the composition depending on the product type desired, and preferably consists of particles having an average size of less than about 150 microns, more preferably about 1 to about 50 microns, and having a specific gravity on the order of about 0.12 to 2.9 gm/cc, more preferably for creams and pastes about 0.12 to about 1.8 gm/cc. A wide variety of silicones, acids and particulate solid stabilizers may be utilized in accordance with the principles of this invention as understood with respect to the following detailed description.